DAKAR, Senegal — Hundreds of Chadians have been killed in attacks by roving groups of Arab gunmen in dozens of villages in the past 10 days, according to aid workers and human rights officials in areas along Chad's troubled border with Sudan.

In all, at least 220 people have been killed, and dozens of wounded people have overwhelmed small, poorly equipped local hospitals, the United Nations said Tuesday. The Chadian government has declared a state of emergency and accused Sudan, its neighbor to the east, of fomenting a crisis.

"By exporting its Darfur conflict to Chad, Sudan wants to weaken Chad by making different Chadian communities fight each other," Hourmadji Moussa Doumgor, a government spokesman, told The Associated Press on Monday. "All this is to prepare the ground for a large-scale war."

Chad and Sudan have traded accusations for more than two years that each country is supporting insurgents across their shared border. Sudan is fighting non-Arab rebel groups in the western region of Darfur that seek greater autonomy for the region, and Chad is fighting rebels seeking to overthrow the regime of Idriss Déby, the current president.

The conflict in Darfur, which pits the non-Arab tribes against the Arab-dominated government, has been marked by brutal violence in which the government has armed Arab militias to fight the non-Arab insurgents. At least 200,000 people have died, and more than 2 million have been driven from their homes. That ethnic warfare has spilled over into Chad, inspiring copycat violence among Chadian Arabs and cross-border raids on villages by Sudanese militias.

The recent violence has been particularly brutal. One man had his eyes gouged out with bayonets, said David Buchbinder, a researcher with Human Rights Watch who is traveling in the region affected by the attacks. Another pair of women were burned alive in their hut, he said.

An error has occurred. Please try again later.

You are already subscribed to this email.

"It is extremely horrific violence," Buchbinder said. "It is as if it is driven by hatred. It is a coordinated action over a large part of eastern Chad, and not always with theft as a motive. Sometimes the motive is only to kill."

The attacks represent a sharp escalation of the violence in the volatile Darfur region and threaten to further destabilize one of the most dangerous and lawless corners of the world.

The attacks appear to be the work of Arab militias from both sides of the Chad-Sudan border, and because they are occurring deep inside Chadian territory, some 100 kilometers, or 60 miles, from the border, the violence is particularly ominous.

The United Nations plans to convene a high-level meeting on Thursday in Addis Ababa, the headquarters of the African Union, to discuss alternatives to end the violence.